JP2007165047A - Proton conductive solid polymer electrolyte and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proton conductive solid polymer electrolyte showing high proton conductivity even in a non-humidified/high temperature condition and having high mechanical strength, and to provide a fuel cell. <P>SOLUTION: The proton conductive solid polymer electrolyte is formed by mixing at least acid and a matrix polymer impregnated with acid, and the matrix polymer has basic polymer structure in a molecule. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a proton conductive solid polymer electrolyte and a fuel cell.

In order to popularize fuel cells, reduction of manufacturing cost is an important issue, and at the same time, high performance and high reliability are required. Therefore, research on hydrocarbon polymer electrolytes has been actively conducted as an alternative to perfluoro-based electrolyte membranes such as conventional Nafion (registered trademark).
Further, many improvements have been made from the viewpoint of extending the life of fuel cells in the market, and in order to solve the problem of carbon monoxide poisoning of the catalyst, the operation temperature is set to a medium temperature such as 100 ° C to 150 ° C. Research on medium temperature polymer solid fuel cells set in the region is also actively conducted. In this case, it is difficult to use water as a proton-conducting medium due to the problem of vapor pressure. As seen in Patent Document 1 (Japanese Patent Publication No. 11-503262), studies using phosphoric acid as a medium and carrier have been made. It is done. In addition, these polymers are generally required to have heat resistance and chemical stability from the viewpoint that the polymer electrolyte must be stably maintained under supply of fuel gas and air at 100 ° C. or higher.

However, the perfluoro-based electrolyte membrane has a drawback that sufficient proton conductivity and output cannot be obtained at an operating temperature of 100 ° C. to 300 ° C. and a relative humidity of 50% or less.
Further, Patent Document 1 discloses a solid electrolyte membrane made of polybenzimidazole doped with a strong acid such as phosphoric acid. In order to obtain a sufficient proton conductivity for fuel cell operation, a polyelectrolyte membrane is used. About 4 to 5 times as much phosphoric acid as the mass of benzimidazole must be contained. Such a membrane having a high phosphoric acid content has low mechanical strength and may cause gas crossover when incorporated in a fuel cell. On the other hand, if the doping rate of phosphoric acid is lowered to increase the mechanical strength of the membrane, there is a problem that proton conductivity is lowered.
Japanese National Patent Publication No. 11-503262

  The present invention has been made in view of the above circumstances, and provides a proton conductive solid polymer electrolyte and a fuel cell exhibiting high proton conductivity even under non-humidified and high temperature conditions and excellent in mechanical strength. The purpose is to do.

In order to achieve the above object, the present invention employs the following configuration.
The proton conductive solid polymer electrolyte of the present invention is characterized in that an acid and a matrix polymer impregnated with the acid are mixed at least, and the matrix polymer has a basic molecular structure in the molecule. To do.
In the proton conductive solid polymer electrolyte of the present invention, the basic molecular structure is preferably a pyridylene group.
Furthermore, in the proton conductive solid polymer electrolyte of the present invention, the matrix polymer has a molecular structure represented by the following general formula (1) containing a urea bond in the molecule within a range of at least 1 mol% to 100 mol%. It is preferable to have. However, in the general formula (1), R ₁ represents a —C ₆ H ₄ —CH ₂ —C ₆ H ₄ — group or a —C ₆ H ₄ —O—C ₆ H ₄ — group (—C ₆ H ₄ -Is a phenylene group) and R ₂ is a pyridylene group.

In the proton conductive solid polymer electrolyte of the present invention, the matrix polymer has a molecular structure represented by the following general formula (2) containing a paravanic acid structure in the molecule in a range of at least 1 mol% to 100 mol%. It is preferable to comprise. However, in the general formula (2), _{R 3} is _{-C 6 H 4 -CH 2 -C 6} H 4 - group or a _{-C 6 H 4 -O-C 6} H 4 - is a radical _(-C 6 _{H 4} -Is a phenylene group) and R ₄ is a pyridylene group.

In the proton conductive solid polymer electrolyte of the present invention, the paravanic acid structure is preferably formed by converting a urea bond in the general formula (1).
In the proton conductive solid polymer electrolyte of the present invention, the matrix polymer may be cross-linked.
In the proton conducting solid polymer electrolyte of the present invention, the matrix polymer may contain a polyparabanic acid resin. The structural formula of the polyparabanic acid resin is, for example, as shown in the following general formulas (3) to (8).
In the proton conductive solid polymer electrolyte of the present invention, the acid is preferably phosphoric acid, phosphonic acid, or a mixture thereof.

Next, the fuel cell of the present invention includes an oxygen electrode, a fuel electrode, and a proton conductive solid polymer electrolyte membrane sandwiched between both electrodes, and an oxidant distribution plate in which an oxidant channel is formed is provided on the oxygen electrode side, In a fuel cell in which a fuel flow plate having a fuel flow path provided on the fuel electrode side is used as a unit cell, the polymer electrolyte membrane is the proton conductive solid polymer electrolyte as described above Features.
In the fuel cell of the present invention, either one or both of the oxygen electrode and the fuel electrode may contain the proton conductive solid polymer electrolyte described in any of the above.

According to the proton conducting solid polymer electrolyte of the present invention, a basic molecular structure is provided in the matrix polymer molecule, and the acid is contained in the matrix polymer by the interaction between the basic molecular structure portion and the acid. Is held stably. Thereby, the proton conductivity of the proton conductive solid polymer electrolyte can be increased.
Further, according to the present invention, a proton conductive solid polymer electrolyte doped with a small amount of acid is used even when the operating temperature is 100 ° C. or higher and 200 ° C. or lower and no humidification or relative humidity is 50% or lower. Thus, it is possible to obtain a solid polymer fuel cell that stably exhibits good power generation performance for a long period of time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
"Proton-conducting solid polymer electrolyte"
The proton conductive solid polymer electrolyte of the present embodiment (hereinafter referred to as polymer electrolyte) is formed by mixing at least an acid and a matrix polymer impregnated with the acid, and a basic molecular structure is present in the matrix polymer molecule. It is provided. As the matrix polymer, an aromatic polyurea resin having a basic molecular structure in the molecule and having a urea bond can be used. Further, a urea-containing polyparabanic acid resin obtained by converting a part of the urea bond in the aromatic polyurea resin into a polyparabanic acid structure may be used. Hereinafter, the aromatic polyurea resin, the urea-containing polyparabanic acid resin, and the acid constituting the polymer electrolyte of the present embodiment will be sequentially described.

[Aromatic polyurea resin]
The aromatic polyurea resin is an aromatic polyurea resin having a basic molecular structure in the molecule. As the basic molecular structure, a pyridylene group can be exemplified, and besides the pyridylene group, quinolylene, quinoxalylene, acridylene and the like can be exemplified.
The specific molecular structure of this aromatic polyurea resin is as shown in the general formula (1). In the general formula (1), R ₁ is a —C ₆ H ₄ —CH ₂ —C ₆ H ₄ — group or a —C ₆ H ₄ —O—C ₆ H ₄ — group (—C ₆ H ₄ — represents By using a phenylene group, the heat resistance of the polymer electrolyte can be improved. Further, by making the R ₂ and pyridylene group, it is possible to stably hold the acid aromatic Poriuea resin. Moreover, an acid can be stably hold | maintained by providing at least 1 mol% or more of the molecular structure shown in General formula (1). Moreover, by providing 100 mol% or less of the molecular structure shown in General formula (1). Further, the solubility in a solvent does not decrease, the moldability by the so-called casting method is improved, and the polymer electrolyte can be easily formed into a desired shape.

The aromatic polyurea resin only needs to have the molecular structure represented by the general formula (1), and other molecular structures may be bonded to the molecular structure. Examples of other molecular structures include those in which a diphenylmethylene group is bonded to a polyparabanic acid structure, and those in which a diphenyl ether group is bonded to a polyparabanic acid structure. Examples of the aromatic polyurea resin having such other molecular structure include those represented by the following general formula (9) or general formula (10). The aromatic polyurea resin represented by the general formula (9) is produced using 4,4′-methylenediphenyl-diisocyanate, 4,4′-diaminodiphenylmethane and 2,5-diaminopyridine as raw materials. The aromatic polyurea resin represented by the general formula (10) is produced using 4,4′-methylenediphenyl-diisocyanate and 4,4′-diphenylether-diisocyanate and 2,5-diaminopyridine as raw materials. .
By combining these other molecular structures, the heat resistance of the polymer electrolyte can be further improved.

[Urea-containing polyparabanic acid resin]
Further, a polyparabanic acid structure can be introduced into the molecule by converting the urea bond contained in the aromatic polyurea resin. The urea-containing polyparabanic acid resin into which the paravanic acid structure is introduced has a molecular structure represented by the general formula (2). Unconverted urea bonds remain in this urea-containing polyparabanic acid resin. That is, the conversion rate is less than 100%. In the general formula (2), R ₃ and R ₄ are the same as those in the general formula (1). The urea-containing polyparabanic acid resin contains the basic molecular structure contained in the aromatic polyurea resin as it is.

  The urea-containing polyparabanic acid resin may have a molecular structure represented by the general formula (2), and other molecular structures may be bonded to the molecular structure. Examples of other molecular structures include those in which a diphenylmethylene group is bonded to a polyparabanic acid structure, or those in which a diphenylether group is bonded to a polyparabanic acid structure, as in the case of an aromatic polyurea resin. Examples of the urea-containing polyparabanic acid resin having such other molecular structure include those represented by the following general formula (11) or general formula (12). The urea-containing polyparabanic acid resin represented by the general formula (11) is obtained by converting the aromatic polyurea resin represented by the general formula (9). The urea-containing polyparabanic acid resin represented by the general formula (12) is obtained by converting the aromatic polyurea resin represented by the general formula (10). By combining these other molecular structures, the heat resistance of the polymer electrolyte can be further improved.

[acid]
The acid in the present embodiment refers to phosphoric acid, phosphonic acid, sulfuric acid, trifluoroacetic acid, trifluoromethanesulfonic acid, trifluoromethanesulfimidic acid, phosphotungstic acid, etc., but heat resistance, corrosiveness, volatility, conductivity From this viewpoint, phosphoric acid and phosphonic acid or a mixture thereof is preferable. Any of these acids interacts with the basic molecular structure or polyparabanic acid structure in the matrix polymer and is impregnated (doped) into the matrix polymer to develop proton conductivity. The acid doping ratio with respect to the matrix polymer is preferably in the range of 5 mol% to 800 mol%, more preferably in the range of 150 mol% to 5001 mol%, although it depends on the type of acid. If the doping rate is too low, the proton conductivity is lowered, which is not preferable, and if the doping rate is too high, the mechanical strength of the polymer electrolyte is reduced, which is not preferable.

[Crosslinked structure]
Moreover, in the polymer electrolyte of this embodiment, the crosslinked structure by the low molecular crosslinking agent may be formed in the matrix polymer. As the low molecular crosslinking agent, a compound selected from a diacid anhydride, a diepoxy compound, and a diisocyanate is preferable. By these low molecular crosslinking agents, a crosslinked structure in which the urea bond portions in the matrix polymer are crosslinked is formed, and the mechanical strength of the polymer electrolyte is further improved. The cross-linking reaction mainly occurs with respect to NH groups in the matrix polymer, and NH groups in adjacent molecular chains are cross-linked to stabilize the molecular structure of the entire matrix polymer.

Examples of the dianhydride include dianhydride pyromellitic acid, cyclobutene dicarboxylic acid anhydride, and derivatives thereof.
Examples of the diepoxy compound include ethylene glycol diglycidyl ether and 2,2′-bis (4-glycidyloxyphenyl) -propane.
Further, as the diisocyanate, diphenylmethane diisocyanate (hereinafter abbreviated as MDI), 4,4′-diphenyl ether diisocyanate (ODI), tolylene diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, hexafluorobiphenyl diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, Examples include isophorone diisocyanate and cyclohexane diisocyanate. Furthermore, these derivatives can also be used.

  Moreover, it is preferable that these low molecular crosslinking agents and a matrix polymer mixing ratio (low molecular crosslinking agent / matrix polymer) are mixed in a ratio of 1/5 (mol / mol) to 1/3 (mol / mol). When the amount of the low molecular crosslinking agent is larger than this, gelation proceeds and it becomes difficult to form the polymer electrolyte into a film.

[Polymer alloy]
In the polymer electrolyte of the present embodiment, the matrix polymer may contain a polyparabanic acid resin. Specifically, it is only necessary that a polymer alloy is formed by an aromatic polyurea resin or a urea-containing polyparabanic acid resin and a polyparabanic acid resin, and the polymer alloy is impregnated with an acid to form a polymer electrolyte. Examples of the polyparabanic acid resin include those having the structures shown in the general formulas (3) to (8).
The content of the polyparabanic acid resin in the polymer alloy is preferably 98% by mass or less, and more preferably 20% by mass or more and 90% by mass or less. When the content is less than 20% by mass, the proton conductivity of the polymer electrolyte is lowered, which is not preferable.

  According to the polyelectrolyte of this embodiment, a basic molecular structure is provided in the molecule of the matrix polymer, and the acid is stabilized in the matrix polymer by the interaction between the basic molecular structure portion and the acid. Held. Thereby, the proton conductivity of the proton conductive solid polymer electrolyte can be increased. In particular, since the basic molecular structure is a pyridylene group, the acid can be held in a more stable form in the matrix polymer.

  In the polymer electrolyte of the present embodiment, those having a paravanic acid structure (urea-containing polyparabanic acid resin) show weak basicity due to the nitrogen atom in the polyparabanic acid structure. For this reason, the interaction with the acid is weaker than in the case of the conventional polybenzimidazole, and the phosphoric acid is not restrained in the matrix polymer and can move relatively freely. Thereby, the polymer electrolyte of this embodiment can show high proton conductivity even with a small amount of acid. Moreover, since the acid content can be lowered, the mechanical strength of the polymer electrolyte can be improved. In addition, since the urea-containing polyparabanic acid resin has a basic molecular structure in the molecule like the aromatic polyurea resin, the acid is stably held in the matrix polymer. Therefore, the polymer electrolyte provided with the urea-containing polyparabanic acid resin has excellent heat resistance and acid retention ability because it has a polyparabanic acid structure, and more excellent because it has a basic molecular structure. Has the ability to retain acid. Thereby, the heat resistance and proton conductivity of the proton conductive solid polymer electrolyte can be increased.

Furthermore, since the matrix polymer is cross-linked, the mechanical strength of the polymer electrolyte can be increased.
Furthermore, the mechanical strength of the matrix polymer can be further increased by forming a polymer alloy by containing a polyparabanic acid resin or the like in the matrix polymer. In addition, since polyparabanic acid has a relatively weak basicity as described above, even when a polyparabanic acid resin or the like is contained, the acid impregnation rate does not decrease and high proton conductivity can be maintained. .

"Production Method of Proton Conducting Solid Polymer Electrolyte"
The method for producing a polyelectrolyte includes a step of synthesizing a matrix polymer, and a step of forming the synthesized matrix polymer into a film shape and impregnating the matrix polymer with an acid.
The method for synthesizing the matrix polymer is described in, for example, literature (E. Scortanu, LNicolaescu, G. Caraculacu, Ldiaconu, and A. Caraculacu, Eur. Polym, J. 34 (1998) 1265-1272). It is synthesized by a method of obtaining an aromatic polyurea resin from the reaction. A synthesis scheme of the aromatic polyurea resin is shown in the following formula (13). In Formula (13), R ₁ represents a —C ₆ H ₄ —CH ₂ —C ₆ H ₄ — group or a —C ₆ H ₄ —O—C ₆ H ₄ — group (—C ₆ H ₄ — Is a phenylene group), R ₂ is a pyridylene group, and n ₁ representing the number of repeating units is a natural number of 10 to 100,000.

As shown in Formula (13), by using diaminopyridine as the diamine, it is possible to introduce a pyridylene group into the aromatic polyurea resin. Further, diaminodiphenylmethane may be used simultaneously with diaminopyridine. In this case, R ₂ in the formula (10) becomes a pyridylene group and a bisphenylmethyl group.
In addition, by using one or both of methylene diphenyl diisocyanate and diphenyl ether isocyanate as the diisocyanate, an aromatic ring can be introduced into the aromatic polyurea resin.

Furthermore, in order to synthesize an aromatic polyurea resin to synthesize a polyurea-containing polyparabanic acid resin, the aromatic polyurea resin is reacted with an oxalyl dichloride (ClOCCOCl) as described in the above document. Is converted to a polyparabanic acid structure. A synthesis scheme of the urea-containing polyparabanic acid resin is shown in the following formula (14). In the formula (14), R ₁ and R ₃ are —C ₆ H ₄ —CH ₂ —C ₆ H ₄ — group or —C ₆ H ₄ —O—C ₆ H ₄ — group (—C ₆ H ₄ -Is a phenylene group), R ₂ and R ₄ are pyridylene groups.
As shown in the formula (14), the aromatic polyurea resin having a basic molecular structure and the urea-containing polyparabanic acid resin are in a relationship between an intermediate and a finished product.

  Next, the synthesized matrix polymer is dissolved in a solvent, a solution is applied onto a substrate such as a glass substrate, and then the solvent is removed by heating to form a polymer film made of the matrix polymer. Examples of the solvent for dissolving the matrix polymer include N-methyl-2-pyrrolidone (NMP). In the case where the matrix polymer is an aromatic polyurea resin, when the solvent is removed by heating, the aromatic polyurea resin is easily oxidized by heat and denatured. Therefore, it is desirable to adjust the heating temperature and the heating atmosphere.

  Next, the matrix polymer is impregnated with an acid by immersing the polymer film made of the matrix polymer in an aqueous acid solution. In this way, a membrane-like polymer electrolyte is obtained.

  Further, when the matrix polymer is dissolved in a solvent and applied on the glass substrate, an acid may be mixed in advance with the matrix polymer and the mixed solution may be applied on the glass substrate. After coating, the solvent is removed by heating in the same manner as described above. In this way, a polymer electrolyte is obtained. According to this method, a polymer film made of a matrix polymer can be formed and simultaneously impregnated with an acid, and the manufacturing process can be simplified.

A polyparabanic acid resin having no basic molecular structure has low acid swellability and insufficient proton conduction. In order to solve this problem, it is necessary to introduce a basic molecular structure into the main chain. However, it is extremely difficult to synthesize isocyanates having a heterocyclic ring such as a pyridylene group, and the literature (TCPatton, Polym. Preprints, 12 (1971) 162-168) and the like, and the synthesis method using hydrogen cyanide was impossible.
In the present invention, a heterocyclic ring is obtained from the reaction of a diamine and a diisocyanate found in the literature (E. Scortanu, LNicolaescu, G. Caraculacu, Ldiaconu, and A. Caraculacu, Eur. Polym, J. 34 (1998) 1265-1272). By synthesizing an aromatic polyurea in the molecule and converting it to parabanic acid, a polyparabanic acid resin having a basic molecular structure in the main chain can be provided without going through a precursor. An aromatic polyurea resin having a heterocyclic ring as a precursor in the molecule also has proton conductivity and can be applied to a fuel cell.
Further, according to the present invention, since the number of reaction steps is one step lower, the polymer electrolyte of the present invention is a material that can be provided to the market at a low cost.

"Fuel cell"
In FIG. 1, the schematic diagram of the single cell which comprises the fuel cell of this embodiment is shown. A single cell 1 shown in FIG. 1 includes an oxygen electrode 2, a fuel electrode 3, and a polymer electrolyte 4 of the present embodiment sandwiched between the oxygen electrode 2 and the fuel electrode 3 (hereinafter referred to as an electrolyte membrane 4). And an oxidant distribution plate 5 having an oxidant flow path 5 a disposed outside the oxygen electrode 2, and a fuel distribution plate 6 having a fuel flow path 6 a disposed outside the fuel electrode 3. The operation temperature is 100 ° C. to 200 ° C. and the humidity is not humidified or the relative humidity is 50% or less.

  The fuel electrode 3 and the oxygen electrode 2 are each generally composed of porous catalyst layers 2a and 3a and porous carbon sheets (carbon porous bodies) 2b and 3b that hold the catalyst layers 2a and 3a. The catalyst layers 2a and 3a contain an electrode catalyst (catalyst), a hydrophobic binder for solidifying and molding the electrode catalyst, and a conductive material.

  The catalyst is not particularly limited as long as it is a metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen. For example, lead, iron, manganese, cobalt, chromium, gallium, vanadium, tungsten, ruthenium, iridium, palladium, platinum, There may be mentioned rhodium or an alloy thereof. An electrode catalyst can be constituted by supporting such a metal or alloy on activated carbon.

  For example, a fluororesin can be used as the hydrophobic binder. Among the fluororesins, those having a melting point of 400 ° C. or less are preferable. Examples of such fluororesins include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride, tetrafluoroethylene / hexafluoroethylene copolymer. A resin excellent in hydrophobicity and heat resistance such as a polymer and perfluoroethylene can be used. By adding the hydrophobic binder, it is possible to prevent the catalyst layers 2a and 3a from being wetted excessively by the water generated in response to the power generation reaction, and the fuel gas and oxygen in the fuel electrode 3 and the oxygen electrode 2 can be prevented. Can be prevented.

  Further, the conductive material may be any material as long as it is an electrically conductive material, and examples thereof include various metals and carbon materials. Examples thereof include carbon black such as acetylene black, activated carbon and graphite, and these are used alone or in combination.

  The catalyst layers 2a and 3a may contain the polymer electrolyte according to the present invention instead of the hydrophobic binder or together with the hydrophobic binder. By adding the polymer electrolyte according to the present invention, the proton conductivity in the fuel electrode 3 and the oxygen electrode 2 can be improved, and the internal resistance of the fuel electrode 3 and the oxygen electrode 2 can be reduced.

The oxidant distribution plate 5 and the fuel distribution plate 6 are made of conductive metal or the like, and function as a current collector by being joined to the oxygen electrode 2 and the fuel electrode 3 respectively. Oxygen and fuel gas are supplied to the pole 3. That is, the fuel electrode mainly containing hydrogen is supplied to the fuel electrode 3 through the fuel flow path 6 a of the fuel flow distribution plate 6, and the oxidant flow path 5 a of the oxidant flow distribution plate 5 is supplied to the oxygen electrode 2. Through this, oxygen as an oxidizing agent is supplied.
The hydrogen supplied as fuel may be supplied by hydrogen generated by reforming hydrocarbon or alcohol, and oxygen supplied as oxidant is supplied in a state of being contained in air. Also good.

  In this single cell 1, hydrogen is oxidized on the fuel electrode 3 side to generate protons, which are conducted through the electrolyte membrane 4 to reach the oxygen electrode 2, and protons and oxygen are electrochemically connected to the oxygen electrode 2. It reacts to produce water and generates electrical energy.

  According to the above fuel cell, it is possible to obtain a fuel cell that stably exhibits good power generation performance for a long period of time even when the operating temperature is 100 ° C. or higher and 200 ° C. or lower and no humidification or relative humidity is 50% or less, It can be suitably used for automobiles, home power generation or portable devices.

Example 1
20 mmol (mmol) of 4,4′-methylenediphenyl-diisocyanate was dissolved in 70 mL of N-methyl-2-pyrrolidone (NMP) at room temperature (solution A). And this solution A is dripped at the solution B in which 10 mmol 4,4'- diaminodiphenylmethane and 10 mmol 2,5- diaminopyridine are melt | dissolved in 70 mL N methyl-2-pyrrolidone (NMP), and it is normal temperature. After stirring for 4 hours, the mixture was further reacted at 80 ° C. for 18 hours.

After the reaction, the reaction solution was mixed with 2000 mL of methanol, and the generated precipitate was filtered. The obtained precipitate (matrix polymer (aromatic polyurea resin)) was washed three times with methanol and vacuum-dried at 60 ° C. The matrix polymer obtained in a yield of 66% had a maroon color, but when redissolved in NMP to a concentration of 10% by mass, a deep red viscous liquid was obtained. In addition, when the molecular weight was separately measured by gel permeation chromatography, the molecular weight was 290,000 in terms of styrene.
A matrix polymer solution was cast on glass to form a deep red polymer film having a thickness of 60 μm. When this membrane was immersed in phosphoric acid having a concentration of 85%, it swelled to 1.95 times its own weight. In this way, the polymer electrolyte of Example 1 was produced.

(Example 2)
The matrix polymer obtained in Example 1 was dispersed in dichloroethane, 3 equivalents of oxalyl dichloride was introduced, and the mixture was refluxed at 60 ° C. for 11 hours (conversion reaction from polyurea to polyparabanic acid). Since the matrix polymer was in a dispersed state, a polyurea-containing polyparabanic acid resin having a heterocyclic ring in the molecule was obtained with a yield of almost 100%. The obtained polyurea-containing polyparabanic acid resin was dissolved in NMP so as to be 10% by mass, and cast into a film on glass. The thickness of the obtained film was 55 μm, and a deep red polymer film almost black was obtained. When this membrane was immersed in phosphoric acid having a concentration of 85%, it swelled to 1.85 times its own weight. In this way, the polymer electrolyte of Example 2 was produced.
In addition, when the proton nuclear magnetic resonance spectrum (400 MHz, DMSO-d6) was confirmed for the polyurea-containing polyparabanic acid resin described above, a peak considered to be a urea bond was confirmed although the peak intensity ratio was small at 8 to 9 ppm. . Therefore, it is considered that some amount of polyurea resin remains in the polyurea-containing polyparabanic acid resin.

(Example 3)
About the polyurea containing polyparabanic acid resin of Example 2, since the peak considered to be urea coupling | bonding was confirmed by the proton nuclear magnetic resonance spectrum (NMR), it was made into NMP so that the polyurea containing polyparabanic acid resin of Example 2 might be 5 weight%. Dissolve, and add 4,4'-methylenediphenyl diisocyanate equivalent to the urea ratio estimated from the NMR integration ratio (about 0.05 equivalent to 1 unit of polyparabanic acid) in an argon gas atmosphere. The mixture was stirred under stirring to be uniformly dissolved, poured into a petri dish, and subjected to a crosslinking reaction while removing the solvent on a hot plate at 80 ° C. The thickness of the obtained film was 90 μm, and the color of the film was almost the same as that of Example 2. When this membrane was dipped in 85% phosphoric acid, it swelled to 1.65 times its own weight. In this way, the polymer electrolyte of Example 3 was produced.

Example 4
After 0.8 g of the matrix polymer prepared in Example 2 and 0.2 g of a polyparabanic acid resin having a molecular weight of about 500,000 using 4,4′-methylenediphenyl diisocyanate synthesized separately are dissolved in NMP, a glass plate is used. Cast film was formed on top (preparation of polymer alloy). The thickness of the obtained film was 70 μm, and the color of the film was almost the same as that of Example 2. When this membrane was immersed in phosphoric acid having a concentration of 85%, it swelled to 1.70 times its own weight. In this way, the polymer electrolyte of Example 4 was produced.

(Comparative Example 1)
Basic molecular structure obtained by cyclization of 4,4'-diphenylmethane diisocyanate with hydrogen cyanide and hydrolysis with concentrated hydrochloric acid with reference to the literature (TCPatton, Polym. Preprints, 12 (1971) 162-168) A polyparabanic acid resin without synthesize was synthesized. The obtained resin was dissolved in NMP to prepare a 10% by mass solution. A cast film was formed using this solution to obtain a transparent film with a light reddish color. The thickness of the membrane was 60 μm, and when this membrane was immersed in phosphoric acid having a concentration of 85%, it swelled to 1.24 times its own weight. Thus, the polymer electrolyte of Comparative Example 1 was produced.

(Comparative Example 2)
At room temperature, 20 mmol of 4,4′-methylenediphenyl-diisocyanate is dissolved in 70 mL of NMP to obtain a solution C, and this solution C is prepared by dissolving 20 mmol of 4,4-diaminodiphenylmethane in 70 mL of NMP. And stirred at room temperature for 4 hours, and further reacted at 80 ° C. for 18 hours.

  After the reaction, the reaction solution was mixed with 2000 mL of methanol, and the generated precipitate was filtered. The obtained precipitate (matrix polymer (aromatic polyurea resin)) was washed three times with methanol and vacuum-dried at 60 ° C. The obtained aromatic polyurea resin (white powder) was dissolved in NMP to prepare a 10% by mass solution. A cast film was formed using this solution to obtain a substantially transparent film. The thickness of the film was 60 μm, and when this film was immersed in phosphoric acid having a concentration of 85%, it swelled to 1.02 times its own weight. Thus, the polymer electrolyte of Comparative Example 2 was produced.

(Evaluation methods)
Infrared absorption spectra of the matrix polymer (aromatic polyurea resin) prepared in Example 1 and the matrix polymer (polyurea-containing polyparabanic acid resin) prepared in Example 2 were measured. The results are shown in FIG.

Moreover, in order to investigate the ionic conductivity of Examples 1-4 and Comparative Examples 1-2, the phosphoric acid on the membrane surface of each polymer electrolyte was wiped off, cut into a circle with a diameter of 13 mm, and this was sandwiched with a platinum plate with a diameter of 13 mm A cell for conductivity measurement was prepared. The AC resistance at 150 ° C. was measured with an impedance analyzer, and the ionic conductivity was calculated from Ohm's law. Moreover, in order to investigate whether the polymer electrolyte of Examples 1-4 and Comparative Examples 1-2 has a power generation characteristic, a single cell was produced using the electrode with a commercially available platinum catalyst (made by E--TEK), the air cathode, hydrogen as a fuel gas was introduced at a flow rate of 100 mL / min to the anode side, while heating the cell to 0.99 ° C., closed at constant current load in open circuit voltage and current density 0.2Acm ^-2 The circuit voltage was examined. The above electrochemical properties are summarized in Table 1.

As shown in FIG. 2, in the matrix polymer of Example 1, a broad absorption peak that appears to be due to NH bonding in the urea bond is confirmed in the vicinity of 3300 cm ⁻¹ . On the other hand, in the matrix polymer of Example 2, the absorption peak due to the NH bond confirmed in Example 1 almost disappears, and instead, a sharp absorption peak that is considered to be due to the carbonyl bond is confirmed near 1740 cm ^−1. . Furthermore, when combined with the NMR results described above, the matrix polymer of Example 2 is considered to be a polyparabanic acid resin in which some urea bonds remain.

  Moreover, as shown in Table 1, about the polymer electrolyte membrane of Examples 1-4, it turns out that both an ionic conductivity and a power generation test result have shown the favorable value. On the other hand, in Comparative Examples 1 and 2, since the basic molecular structure was not introduced into the matrix polymer, the doping amount of phosphoric acid was greatly reduced as compared with Examples 1 to 4, and thereby the ionic conductivity was reduced. It is considered that both the power generation test results and the power generation test results have decreased.

FIG. 1 is a schematic cross-sectional view showing the structure of a single cell of a fuel cell according to an embodiment of the present invention. FIG. 2 is an infrared spectrum of the matrix polymer in Example 1 and Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Single cell (fuel cell), 2 ... Oxygen electrode (electrode), 3 ... Fuel electrode (electrode), 4 ... Electrolyte membrane (proton conductive solid polymer electrolyte)

Claims (9)

  A proton-conducting solid polymer electrolyte, wherein an acid and a matrix polymer impregnated with the acid are mixed at least, and the matrix polymer has a basic molecular structure in the molecule.   The proton conductive solid polymer electrolyte according to claim 1, wherein the basic molecular structure is a pyridylene group. 2. The matrix polymer according to claim 1, wherein the matrix polymer has a molecular structure represented by the following general formula (1) containing a urea bond in the molecule in a range of at least 1 mol% to 100 mol%. 3. The proton conductive solid polymer electrolyte according to 2.
However, in the general formula (1), R ₁ represents a —C ₆ H ₄ —CH ₂ —C ₆ H ₄ — group or a —C ₆ H ₄ —O—C ₆ H ₄ — group (—C ₆ H ₄ -Is a phenylene group) and R ₂ is a pyridylene group.

The matrix polymer has a molecular structure represented by the following general formula (2) containing a paravanic acid structure in the molecule in a range of at least 1 mol% to 100 mol%. Item 4. The proton conductive solid polymer electrolyte according to any one of Items 3 to 4.
However, in the general formula (2), _{R 3} is _{-C 6 H 4 -CH 2 -C 6} H 4 - group or a _{-C 6 H 4 -O-C 6} H 4 - is a radical _(-C 6 _{H 4} -Is a phenylene group) and R ₄ is a pyridylene group.

  5. The proton conductive solid polymer electrolyte according to claim 4, wherein the paravanic acid structure is formed by converting a urea bond in the general formula (1).   The proton conductive solid polymer electrolyte according to any one of claims 1 to 5, wherein the matrix polymer is crosslinked.   The proton conductive solid polymer electrolyte according to any one of claims 1 to 6, wherein the matrix polymer contains a polyparabanic acid resin.   Provided with an oxygen electrode, a fuel electrode, and a polymer electrolyte membrane sandwiched between both electrodes, an oxidant distribution plate having an oxidant flow path formed on the oxygen electrode side, and a fuel flow distribution plate having a fuel flow path formed on the fuel electrode side 8. A fuel cell having a unit cell as a unit cell, wherein the polymer electrolyte membrane is the proton conductive solid polymer electrolyte according to any one of claims 1 to 7. The proton conductive solid polymer electrolyte according to any one of claims 1 to 7, wherein either one or both of the oxygen electrode and the fuel electrode includes the proton conductive solid polymer electrolyte. Fuel cell.

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